1. Field of the Invention
The invention relates to a flash memory. Particularly, the invention relates to a flash memory and a memory cell programming method thereof.
2. Description of Related Art
Since a flash memory has advantages of non-volatile, high density and fast response speed, etc, it becomes popular in various memories. Data storage of a memory is closely related to device reliability. In recent years, various data programming methods of the flash memory are provided to improve reliability of the flash memory.
When the flash memory is programmed, a high voltage is generally used to program data, though due to variations of the semiconductor manufacturing process, programming voltages required by memory cells in the flash memory are different. In order to correctly program data to each memory cell, a conventional method is to increase the programming voltage, though such method has a risk of reducing the reliability of the flash memory. FIG. 1 is a schematic diagram of a memory cell array of a conventional flash memory. As shown in FIG. 1, when a high voltage is applied to a bit line BL to program a memory cell 102, a memory cell 104 is also influenced by the high voltage, and electrons in the memory cell 104 gradually outflow from a drain, which influences the reliability of the flash memory. Moreover, by using the high programming voltage to program data to the flash memory, besides the reliability of the flash memory is influenced, disadvantages of wasting power, increasing a circuit area, and reducing a service life of the flash memory are also encountered.